Electrolyte transport in rabbit cecum. I. Effect of RDEC-1 infection.

To investigate the characteristics of intestinal ion and fluid secretion induced by the adherent, effacing enteropathogenic Escherichia coli strain RDEC-1, we infected weanling rabbits with 10(7)-10(8) RDEC-1 organisms and then studied cecal ion transport under short-circuit conditions in Ussing chambers. Results in tissues with confluent adherent organisms were compared with those in uninfected ceca and in ceca stimulated with dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP). The short-circuited cecum normally absorbed Na and Cl, secreted bicarbonate (as represented by the residual ion flux), and displayed a high rate of nondiffusional Na and Cl transport. RDEC-1 infection did not alter the short-circuit current (Isc), but it increased the conductance (Gt), decreased the potential difference (PD), abolished net Na absorption, and reversed Cl absorption to secretion. The changes in Na and Cl net fluxes may be explained by inhibition of a Na-Cl linked absorptive process. In contrast, DBcAMP significantly increased the Isc, PD, and Gt, decreased net Na flux, and abolished net Cl absorption by stimulating electrogenic Cl secretion. These results suggest that RDEC-1-induced changes in cecal ion transport are not mediated by cAMP. The reduction in Na-Cl linked absorption is consistent with anatomic changes in the apical surfaces of absorptive epithelial characteristic of effacing enteroadherence, whereas the increased conductance is consistent with tight junction disruption seen with RDEC-1 infection.

Managing the cancer risk in chronic ulcerative colitis. A decision-analytic approach.

Chronic ulcerative colitis is associated with a high risk of colon cancer. The most appropriate management--prophylactic proctocolectomy or medical surveillance--is, at present, unclear. Recent reports suggest that the presence of colonic dysplasia or "precancer" on endoscopic biopsy may be a reliable predictor of concurrent or future colon cancer. To assess the value of colonic dysplasia in managing colitis patients, I applied decision analytic techniques to currently available data regarding the sensitivity and specificity of colonic dysplasia in colitis patients. Such analysis shows that management based on biopsy for colonic dysplasia, rather than prophylactic proctocolectomy for all colitis patients, will maximize 5-year survival. Sensitivity analysis suggests that management is primarily determined by the sensitivity of biopsy-diagnosed dysplasia--elective prophylactic surgery would be preferred only when sensitivity of dysplasia on biopsy is less than or equal to 0.70 at 20 years, or less than or equal to 0.85 at 30 years of colitis, and changing surgical mortality and survival benefit from early diagnosis within a range established by previous studies affects management decisions only when sensitivity of dysplasia is at the lower end of its reported range.

Diverticulitis complicated by candidal pylephlebitis.

A 58-year-old woman had fever, diarrhea, and polymicrobial bacteremia that progressively worsened despite appropriate antibiotic therapy. At autopsy, a diverticular abscess and pylephlebitis were found, both demonstrating hyphal forms consistent with Candida on microscopy.

Ischemic colitis complicating sickle cell crisis.

Abdominal pain is quite common in sickle cell crisis, although the cause of abdominal pain is seldom determined and remains controversial. We have recently seen an 18-yr-old man with sickle cell disease who developed acute abdominal pain during a crisis. Rebound tenderness on physical exam and "thumbprinting" on barium enema examination suggested possible colon infarction. Histopathologic review of the resected ascending colon demonstrated mucosal necrosis and submucosal edema consistent with ischemic colitis. Hypotheses regarding the cause of abdominal pain in sickle crises are reviewed; the pathophysiology of sickle-cell induced vasocclusion and its relation to the development of ischemic colitis in our patient is discussed.